Schedule 40 & 80 Conduit FAQs

A customer is questioning the use of schedule 40 PVC conduits through a roof. They are concerned with the conduit melting at the point it penetrates the roof due to heating by the sun. At what temperature would the surface of the roof need to reach to cause this?

Article 352(D) of the National Electrical Code states that it has a maximum ambient temperature of 122 deg. F. We have known PVC conduit to be used in many on the roof applications. The biggest worry there has been the use of expansion joints.

A question of the strength of a glued elbow, in particular on 3" Schedule 40 PVC; how many pounds of force are needed to separate a joint? Will the joint just pull apart or break?

A properly solvent cemented joint will become the strongest part of a conduit assembly and can withstand direct pulls in excess of 1000 pounds per foot. We have seen failures, as breakage, during testing that occurred with the conduit. In the field it is common to see couplings pull apart or pull out of boxes by breaking their locknuts. This is usually caused by the contraction of the conduit do to temperature changes and the lack of expansion fittings.

Assuming a straight 10' length of schedule 80 conduit how much flexure is acceptable or can safely be obtained without kinking the conduit? If one end is at zero and fixed how much bend can I put in the piece? How many inches off would the other end be?

We are not sure. PVC Conduit does not kink because of its yield strength. Instead it will break when over bent. Also, it is possible to take 60 feet of conduit and make a 90 degree bend without the use of heat. This is know as cold field bending. Refer to NEMA TCB-2 for additional information on cold field bending. All PVC conduit is required to be supported when exposed per Section 352.30 of the National Electrical Code.

Can Sch 40 be run vertical in a building between floors?

Yes, Schedule 40 is permitted to run vertical between floors. If the floor is fire rated than a Certified Fire Stop will have to be used at the penetration.

Can Sch 40 Electrical Conduits be used in interior building environments? Can Sch 40 Electrical Conduits be located in Return Air Plenums? Same questionregarding warehouses & industrial interior environments?

Yes, ETL listed Schedule 40 PVC can be used in interior building environments, warehouses, & industrial interior environments. In fact, it can even be used behind or can penetrate fire-rated walls, provided a firestop is used. Article 352 of the National Electrical Code governs the use of Schedule 40 and 80 PVC Conduit in aboveground (interior or exterior), direct burial, or concrete encasement applications. No, PVC cannot be used in air handling plenums.

Do you have anything in writing that would state the fire rating of Schedule 40 conduit?

Schedule 40 PVC Conduit does not have a fire-rating but can be used in fire-rated construction.

Do you have or know of a conduit fill calculator for PVC?

For electrical applications, the National Electrical Code offers wirefill tables in Chapter 9.

How can you tell if Schedule 40 PVC pipe has been recycled?

How do you mean, "Recycled"? Like taken from an old installation to a new installation? We have print codes on our conduit that can tell us when it was made. Conduit does not sit in our yards for a long time.  In addition, conduit needs to be solvent cemented together at the joints. Have all the integral bells been cut off? This would be an easy way to tell the conduit is being reused. If you have any elbows in question look for wear on the inside wall due to cable pulling.  I guess it is one of those things "You know it when you see it".

How long can your conduit remain exposed to direct sunlight before it becomes damaged, brittle, and unable to protect the service?

Our listed Schedule 40 and 80 PVC Conduit has been evaluated for sunlight exposure by ETL per UL651 and in accordance to Section 352.  The PVC Conduit utilizes UV inhibitors and has an indefinite life when used in exposed applications where direct sunlight is present.

I am working on a project that has exposed conduit subject to winter temperatures - is there a low temperature that PVC conduit is not recommended?

PVC conduit does not have a low temperature limit. When PVC is exposed to very low temperatures it will become more brittle. This is only a problem when it gets impacted. Since Schedule 40 PVC conduit is not allowed to be use in areas of physical damage (Section 352)  this should not be a problem.

Schedule 80 PVC Conduit is listed for uses in areas of physical damage and has been used in impact areas of low temperatures throughout the years without a problem. We always recommend erring on the side of safety. If you believe that low temperatures and areas of impact are going to be a problem use a metal conduit. I rather you call me and tell me you did not use our product, than call me with a failure.

I have a contractor who needs to know about disposing of Schedule 40 pipe. Does it go in the recyclable or to a land fill?

Since the PVC will not decompose it is not ideal for landfills. It however will not cause any damage to drinking water. Since PVC is a recyclable material it should be recycled whenever possible. There should be a local PVC recycling center near your contractor.

I have a contractor who would like to know if primer must be used when connecting Sch40 PVC. In other words, will PVC cement work without the primer and is it considered to be installed correctly without the primer?

The National Electric Code does not require primer to be used in addition to PVC solvent cement. However, primer will aid the assembly and ensure the quality of the joint, as it better prepares the joint for solvent cementing.

Contact your solvent cement and primer manufacturer for additional information.

I have a customer looking for some kind of spec that states what the Fire rating as well as the Fire Spread rating is on Schedule 40.

PVC conduit is not fire rated like an outlet box would be. When conduit penetrates a fire wall assembly the fire stop that is used is classified for the conduits it can be used with. Listed PVC Conduit is "Flame Retardant" per Section 352.100 of the NEC. The flame testing is found in the product standard UL651. Our product is ETL listed to UL651. Listed PVC conduit is not capable of conveying a flame. PVC is a self-extinguishing material that does drop flaming particles.

I have a customer that is under the impression that schedule 40 PVC conduit installed underground should never have water in it. It has always been my impression that PVC conduit installed underground is not a 100% watertight installation nor is it meant to be.

All conduits and ducts, whether they are nonmetallic or metal, will get moisture in them. The moisture gets in through leaky joints or condensation. That is why the National Electrical Code started to require that all conductors or cables be listed for a "Wet Location".  See section 300.5 of the NEC.

I have an existing Sch 80 pipe installed and they are connecting Sch 40 pipe to the Sch 80. Because of the different I.D. there is a small lip where the two connect. Is there an adapter to make the uneven surface less uneven?

No, they will just have to ream the conduit to account for the step between the conduit sizes.

What is the minimum bending radius for Schedule 40 conduit?

The minimum-bending radius for schedule 40 conduits is found in Table 2, Chapter 9 of the NEC.  Also refer to Article 352 of the NEC for bend information.

I just had an individual call and they are redoing an old home and want to use Sch 40 PVC in the walls. Is this an approved application?

PVC Schedule 40 is approved to be used indoors. It can be used behind wall or on the surface of the wall (provided it's not subject to physical damage). If it penetrates a fire wall, it has to be firestopped. Article 352 of the National Electrical Code governs the use of PVC conduit.

I received a call from a local engineering firm. They are running conduit under a bridge in a high voltage application. Anyway, they are considering using either fiberglass or PVC and have asked what are the advantages to using the PVC over the fiberglass for this application.

Fiberglass is usually used in bridge crossing because they can have a larger distance between support. In addition, fiberglass is available for bullet resistance. People will shoot at the pigeons under bridges.  Besides those two facts there is not an advantage for one over the other.

I was wondering whether or not rigid PVC was suitable for a greenhouse application where the overall temperature could range from 90-120 degrees Fahrenheit. Please advise, and if so what installation methods are recommended to the contractor (i.e. expansion couplings, etc.).

Absolutely...PVC conduit has been used in lots of greenhouses. You do require expansion joints though to account for the temperature differential.

In reading through technical information on the website regarding temperature limitations for your schedule 40 and 80 PVC conduit, I understand the conduit is rated for use with 90 degree C conductors but it is only rated for 50 degree C ambient. If the conduit can withstand 90 degree C conductors at their full 90 degree C ampacity, why is the conduit not rated for more than a 50 degree C ambient? It seems that if the conductor temperatures are 90 degree C, the outside of the conductor insulation would be at least above 50 degree C (the conduit rating).

The ambient temperature rating is based on 10 deg. C less than the Relative Thermal Index (RTI) of the plastic. In this case, the generic RTI for PVC is 60 deg. C, so the maximum ambient temperature is 50 deg. C.

It is our experience that it is not unusual to get water seepage into underground PVC conduits. Please confirm that this is the case.

Water does not seep through the PVC itself. All conduits in underground applications get moisture in them. That is why the NEC requires conductors and cables to be listed for a wet location.

My question concerns what the standard is for sunlight resistance? We are a Florida based Electrical Contractor and a question as to how long PVC conduit can withstand direct sunlight before it will start to break down has been a topic of discussion. Summer heat and humidity is extremely harsh on everything down here and I wonder if there is a rule of thumb for determining the time that PVC will last in this environment or is this just something not to be concerned with?

UV is an issue for all plastic products. Fortunately there are additives that are added to plastics to make the material UV resistance. ETL Listed Schedule 40 and 80 PVC conduit utilizes these additives and are UV resistant. The sunlight resistance test is found in UL Standard UL651. Our product is ETL List to UL651. Listed Schedule 40 and 80 Conduit have been used in Florida for years including on rooftops. It is preferred along the coast because it is corrosion resistant. When used in an exposed environment where there are changes in temperatures please are sure to use enough expansion fittings.

Please advise if you have any installation instructions for bending PVC in the field.

PVC conduit manufacturers recommendation are to follow the procedure provided by the manufacturer of the PVC bending equipment.

Under what conditions would Sch. 40 or 80 RNC be suitable per mfg instructions as a support for cable that is ran on the outside of the installation and tie wrapped to the conduit. For example does Prime Conduit's listing instructions allow a No. 4 copper conductor attached to the exterior for it’s length to be in compliance with the provisions of Article 300.11 (B) of the NEC?

Schedule 40 and 80 PVC Conduit is not identified in its listing as a means of support for other raceways, cables or conductors as described in 300.11(B). Therefore the No 4 copper conductor is not permitted to be supported by the raceway on the exterior of the product.

We disagree as to whether the inside of rigid nonmetallic conduit is considered a wet location when installed underground or in a slab or concrete in direct contact with the earth. What is your understanding of this?

All conduits (raceways), whether they are metal or nonmetallic, installed in underground locations are considered a wet location. In fact, the National Electrical Code has adopted language for Section 300.5(B) to say: "Insulated conductors and cables installed in these enclosures or raceways in underground installations shall be listed for use in wet locations and shall comply with 310.10(c)"  Moisture can enter the raceway because of leaky joints and/or due to condensation that occurs to the heating and cooling of the conductors.

We have a contractor who is using Sch 40 conduit inside of a cinder block wall as a sleeve for MC Cable. The wall is a 2 hour fire rated wall and the inspector is saying PVC can not be used inside the fire rated wall. My understanding is it can be used inside the wall and the only issue is where there are penetrations and at that point we need to firestop.

Schedule 40 is permitted to be used in fire-rated walls. If it penetrates a fire rated wall, a fire-stop must be used.

What is the Intertek / ETL mark?

Prime Conduit is pleased to announce the addition of Intertek/ETL to our family of Nationally Recognized Testing Laboratories (NRTLs). You will now see the ETL Listing mark on our conduit and elbows. Prime Conduit customers are accustomed to seeing the UL listing mark and CSA certification mark on our many products. At this time, we would like to introduce the ETL mark to our Schedule 40, Schedule 80, and EB 20 Conduit and Elbow product lines. Nearly every installation falls under the jurisdiction of some regulatory agency. Most of the electrical installations are regulated by state, local and national installation codes. The most commonly used Regulations are found in the National Electrical Code (NEC). Rigid PVC conduit and elbows are covered by Section 352.6 states “Listing Requirements. PVC conduit, factory elbows, and associated fittings shall be listed.” Listing can be provided by any OSHA approved NRTL. A Nationally Recognized Testing Laboratory (NRTL) is an independent laboratory recognized by the Occupational Safety and Health Administration (OSHA) to test products to the specifications of applicable product safety standards – such as those from Underwriters Laboratories (UL), CSA, NSF and other standards – writing bodies. A NRTL’s function is to provide an independent evaluation, testing and certification of any electrically operated product. For more information regarding Nationally Recognized Testing Laboratories go to: http://www.osha.gov/dts/otpca/nrtl/.

Do you have any pipe stiffness data for your Schedule 40 and 80 Conduit?

Unfortunately Prime Conduit does not have listed PSI ratings for our Schedule 40/80 ETL listed PVC Conduit.  Our Sch 40/80 ETL listed conduit meets NEMA TC2 and UL651 requirements, in regards to crush testing requirements.  Furthermore, our products do not have an internal PSI rating as they are not intended for transfer of any fluids or gases.

What is the crush rating of Schedule 80 conduit?

The crush rating is listed in UL651.  Our ETL listed Sch 80 meets the crush requirements of section 6.9 and table 6.3 per the UL651 standard.  For sizes 1/2" - 6" it shall not deflect more that 30% at a load of 2000lbs/force.

What is the crush rating for your Schedule 40 conduit?

The crush rating is listed in UL651.  Our ETL Listed Sch 40 conduit meets the crush requirements of section 6.9 and table 6.3 per the UL651 standard. 

It shall not deflect more that 30% at the following lbs/force loads:

Trade Size

Schedule 40

1/2"

1000 lbf

3/4"

1000 lbf

1"

1000 lbf

1-1/4"

1000 lbf

1-1/2"

750 lbf

2"

700 lbf

2-1/2"

1000 lbf

3"

1000 lbf

3-1/2"

1000 lbf

4"

900 lbf

5"

850 lbf

6"

850 lbf

What is conduit's Schedule B code?

Per the 2013 Schedule B Book, PVC conduit is 3917230000 (TUBES, PIPES & HOSES, RIGID, OF POLYMERS OF VINYL CHLORIDE)

39.17 - Tubes, pipes and hoses, and fittings therefor (for example, joints, elbows, flanges), of plastics:

3917.23.0000 - - - Of polymers of vinyl chloride

Click on the following link to search the latest information:

http://www.census.gov/foreign-trade/schedules/b/index.html

What is your conduit's ECCN number?

ECCN, stands for Export Control Classification Number. An ECCN is an alpha-numeric classification used in the Commerce Control List to identify items for export control purposes. An ECCN is different from a Schedule B number, which is used by the Bureau of Census to collect trade statistics. It is also different from the Harmonized Tariff System Nomenclature, which is used to determine import duties.

A Customer Service Rep. told Prime Conduit that conduit's ECCN number falls in the "catch all" category of EAR99.

Click on the following link for additional information regarding ECCN numbers:

http://www.bis.doc.gov/licensing/do_i_needaneccn.html#qfour

 

Where can I find an MSDS for Conduit and Fittings?

MSDS are not provided for conduit, elbows, or fittings, etc. because those products are an "article" under the OSHA Hazard Communication Standard (HSC), 29 CFR 1910.1200.

 

The Hazard Communication Standard has an exemption for articles.  To fall under the article exemption, the product must be a manufactured item:  (1) which is formed to a specific shape or design during manufacture; (2) which has end-use functions dependent in whole or in part on its shape or design; and (3) which does not release, or otherwise result in exposure to, a hazardous chemical under normal conditions of use.  The PVC conduit, elbows, or fittings, etc. produced by Prime Conduit meet all of these criteria and, consequently, are exempt from the Hazard Communication Standard.

 

Please refer to the following web page for more information:

http://www.osha.gov/

Rodent attack on PVC conduit or duct

We are often questioned on the possibility of a rodent (groundhog, rat, etc...) Chewing through direct buried or exposed pvc conduit and duct.  We have responded to these questions by assuring our customers that pvc conduit or duct is not a source of nutrition,  therefore is not subject to the attack of rodents.

 The National Sanitation Foundation (NSF) conducted a series of tests designed to determine the susceptibility of PVC sewer pipe to attack by rodents.  [1]  PVC pipe was cut into sections and were installed in the openings of a rat enclosure as a barrier between the rats and sources of food and water.  The rats were supplied with reduced rations of food calculated to maintain good health but constant hunger.  After one month period of testing the pvc pipe sections showed evidence of the rats attempts to gnaw through to obtain the additional food,  but there was no penetration of the pipe.  There is no evidence of an attempted attack on the pipe when it did not interfere with access to food.

 It should also be noted that rodents will chew on anything to keep their teeth sharp and to control the length of the teeth.




[1] “A STUDY OF PLASTIC PIPE FOR POTABLE WATER SUPPLIES,”  NATIONAL SANITATION FOUNDATION,  HEADQUARTERS:  SCHOOL OF PUBLIC HEALTHUNIVERSITY OF MICHIGAN,  ANN ARBOR, MI (JUNE 1955) PGS. 80-83

What ASTM test does your conduit meet?

Prime Conduit's conduit meets several different ASTM tests.  However, the primary one that is most referenced is ASTM D 1784.  Our conduit is ETL Listed to UL651.  UL651 states “The compound of which rigid PVC conduit and fittings are made shall be as described in Standard Specifications for Rigid Poly(Vinyl Chloride) (PVC) Compounds and Chlorinated Poly(Vinyl Chloride)  (CPVC) Compounds, ASTM D 1784.”  Therefore, because it is ETL Listed to UL651, it meets ASTM D 1784.

ASTM 1784 - Standard Specification for Rigid Poly(Vinyl Chloride) (PVC) Compounds and Chlorinated Poly(Vinyl Chloride) (CPVC) Compounds